To meet challenges in future competition and avoid being pipelined, a telecommunications operator attaches more importance to a network functions virtualization (NFV) technology. In the NFV technology, the operator processes a service packet using processing software and a service processing unit (also referred to as a network element), so as to provide a service for a user (or a terminal device on which client software for implementing a service function is installed) that sends the packet.
Moreover, to enhance competitive strength, the operator gradually increases frequency of updating services (or the processing software of the service processing unit). In addition, services in the telecommunications field have a relatively high requirement on reliability. For example, it is required that a service interruption time every year should be less than a specified value (for example, five minutes). Therefore, in the NFV technology, it is required that services should not be interrupted in a software upgrade process of the service processing unit.
To meet the foregoing requirement, in an existing NFV system, a master board and a slave board are generally configured for a service processing unit. Normally, the master board is configured to process a service packet sent by a terminal device. During an upgrade of the master board, the slave board takes over the job of the master board. During an upgrade of processing software of the service processing unit, first, processing software of the slave board is upgraded. After the upgrade of the processing software of the slave board is completed, service processing is handed over from the master board to the slave board, and then processing software of the master board is upgraded. After the upgrade of the processing software of the master board is completed, service processing is handed over from the slave board to the master board. In this way, a software upgrade is implemented without interrupting services.
However, in the foregoing technology, when the master board and the slave board are put into operation after the upgrade of the processing software is completed, that is, started after the upgrade, all service packets are processed by the master board or the slave board whose processing software is upgraded. For example, when there is a defect in a new version, service access of all users may be affected.